Self-propelled tree delimber

ABSTRACT

A self-propelled tree delimber includes a horizontal T-shaped frame having a length suitable for supporting full-length trees of medium size. A boom and grapple assembly is mounted on the head portion of the frame and is operable for lifting cut trees from the ground and placing them on the frame. A delimbing assembly is mounted for movement along tracks extending the length of the leg portion of the frame and includes pivoted blades arranged to receive and encircle the stem of a tree, when the tree is placed on the frame. A drive motor is mounted on the head portion of the frame and is drivingly connected to the delimbing assembly for propelling the assembly along the tracks to delimb any tree stem encircled by the blades. The leg portion of the frame is supported on a driven steerable wheel and the head portion of the frame is supported on a pair of driven wheels which are mounted for movement between working and transport positions for respectively moving the delimber perpendicular and parallel to its length. The leg portion of the frame is constructed in two sections which are disconnectible for shortening the length of the delimber for transport.

United States Patent [1 1 French et al.

Sept. 1-1, 1973 SELF-PROPELLED TREE DELIMBER [75 Inventors: John Lischer French, Moline, 1.; Kenneth Quentin Kessler, Dubuque, Iowa; Walter W. Funk, Fresno, Calif; Victor Charles Pierrott, III; Stanley Hiseler, both of Dubuque, Iowa [73] Assignee: Deere & Company, Moline, Ill.

[22} Filed: July 27, 1972 21 Appl. No.: 275,719

Related US. Application Data [62] Division of Ser. No. 120,501, March 3, I97].

[52] U.S."Cl. 144/2' Z, 144/309 AC [51] Int. Cl. A0lg 23/00 [58] Field of Search 144/2 Z, 3 D, 309 AC [56] References Cited 7 UNITED STATES PATENTS 3,461,928 8/1969 Siiro 144/3 D Primary Examiner-Gerald A. Dost Attorney-H. V. Harsha et al.

[57] ABSTRACT A self-propelled tree delimber includes a horizontal T- shaped frame having a length suitable for supporting full-length trees of medium size. A boom and grapple assembly is mounted on the head portion of the frame and is operable for lifting cut trees from the ground and placing them on the frame. A'delimbing assembly is mounted for movement along tracks extending the length of the leg portion of the frame and includes pivoted blades arranged to receive and encircle the stern of a tree, when the treeis placed on the frame. A drive motor is mounted on the head portion of the frame and is drivingly connected to the delimbing assembly for propelling the assembly along the tracks to delimb any tree stem encircled by the blades. The leg portion of the frame is supported on a driven steerable wheel and the head portion of the frame is supported on apair of driven wheels which are mounted for movement between working and transport positions for respectively moving the delimber perpendicular and parallel to its length. The leg portion of the frame is constructed in two sections which are disconnectible for shortening the length of the delimber for transport 11 Claims, 15 Drawing Figures PATENTED SEP] 1 I975 saw .701- ur ii PATENTEU SEN 1 I915 saw on or 1:1'

PATENTEUSEP! nan sum :Ios ur 1'1 PATENTEDSEPI 1 ms sum as m 11 PATENTEDSEH 1 I973 SHEET .08 0F 11 PATENTEDSEPI 1 I915 3.751. 8337 saw us or 11 FIGJO PATENTEDSEP! H 3.757. 837

sum 11 or n die and effectively delimb a I SELF-PROPELLED TREE DELIMBER CROSS REFERENCE TO RELATED APPLICATION This is a division of application Ser. No. l20,501, filed Mar. 3, 1971.

BACKGROUND OF THE INVENTION The present invention relates to a tree delimber and more particularly relates to a self-propelled delimber for handling full-length felled trees.

Tree harvesting is often carried on where the topography and/or the condition of the terrain are adverse to vehicle mobility over the terrain. In such cases, it is common practice to first fell the trees, and then to skid the trees to a relatively level landing area where the trees are left in piles. Trees, when piled, are very difficult to delimb by manual means, such as chain saws, since the limbs are entangled. Known mechanical delimbers are either not suited for working on trees in a pile or they lack maneuverability and the ability to hanfull-length tree in an efficient manner. I

SUMMARY OF THE INVENTION According to the present invention there is provided a delimbing vehicle for delimbing full-length felled trees.

It is a broad object of the invention to provide a vehicle whichis particularly suited for working on trees which have been piled. More specifically, it is an object to provide a vehicle which is self-propelled and which is maneuverable for working alongside trees piled at a landing area.

Another object is to provide a delimber having a delimbing platform long enough for supporting substantially the entire length of a tree and being constructed of two sections, which are disconnectible for shortening the frame for transport. Another object is to provide a vehicle wherein a power unit including an operators station is fixed to one end of the delimbing platform and wherein an operator at the station has a clear view of the operations being performed.

Still another object is to provide a delimbing vehicle having a novel blade assembly for encircling and delimbing a tree stem. 1

These and other objects will become apparent from the ensuing description andappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an oblique perspective view of a self- FIG. 6 is a perspective view of the steering mechanism for the support wheel mounted on the elongated leg portion of the T-shaped frame.

FIG. 7 is a side view of the delimbing platform showing the disconnectible joint therein.

FIG. 8 is an oblique perspective view of the delimbing head showing the blade assembly in the closed con-. dition.

FIG. 9 is a view similar to FIG. 8 but showing the blade assembly in the open condition.

FIG. 10 is a perspective end view of the delimbing head shown in FIG. 8.

FIG. 11 is a perspective side view of the delimbing head shown in FIG. 8.

FIG. 12 is a perspective side view showing the parts of the blade assembly and the blade-opening mechanism which cooperate during the opening of the blades.

FIG. 13 is an end view of the delimbing head showing one of the spring assemblies for biasing the delimbing blades toward a tree stem.

FIG. 14 is a right side perspective view of the topping mechanism.

FIG. 15 is a left side perspective view of the topping mechanism.

' DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, there is shown a generally T-shaped, self-propelled delimbing machine 10. The machine 10 includes a power. unit 12 forming the head of the machine and having a generally horizontal frame 14 in which is fixed one end of an elongated, generally horizontal delimbing platform 16, which forms the leg of themachine. The frame 14 is supported on a pair of ground wheels 18 and 19 located under the opposite ends thereof, and the platform 16 is supported on a ground wheel 20 located approximately midway between its ends, thus leaving a substantial portion of the platform cantilevered beyond the wheel 20.

The wheels 18, 19 and 20 are individuallydriven and are tumable between a working position (FIG. 1), for advancing the machine 10 perpendicularly to the length of a pile of felled trees, and. a transport position, for advancing the machine 10 parallel to its length.

For this purpose, the wheels '18 and 19 are swivelly mounted by means of vertical spindles 22, which are rotatably received in receptacles 24 under the opposite ends of the frame 14. The spindles 22 are fixed to the tops of brackets 26 which are integral with drive housings'28, which are in turn fixed centrally to the wheels 18 and 19. A pair of reversible hydraulic motors 30 are mounted on the brackets 26 and include drive or outpropelled delimbing vehicle constructed according to i the principles of the present invention.

FIG. 2 is a perspective view of the operator's station and'tree-handling boom and grapple assembly of the vehicle.

FIG. Bis a view similar to FIG. 2 but taken from the opposite side of the vehicle.

FIG. 4 is a perspective view showing the vertical piv- I otal connection of the tree-handling boom and grapple assembly.

FIG. 5 is a front planview of the delimber showing the support wheels in their transport position and schematically showing the main pump and the motor for driving the delimbing head.

put shafts which extend through a tube 32 to a drive, for the wheels, located in the housings 28. Remotely operable pins (not shown) are selectively engageable with aligned apertures in the frame 14 and the brackets 26 to lock the brackets to the frame to hold the wheels 18 and 19 either in their working or transport positions.

34 which is rotatably received in a receptacle 36 fixed to the side of the platform 16. The spindle 34 is fixed to the top of a bracket 38, which is integral with a drive housing 40, which is in turn fixed centrally to the wheel 20. A reversible hydraulic motor 42 is mounted on the bracket 38 and includes a drive or output shaft which extends through a tube 44 to a wheel drive in the housing 40. The wheel 20 is steerable between its working and transport positions by structure including a sprocket 46 fixed coaxially on the spindle 34 and having a length of roller chain 48 meshed therewith. The opposite ends of the chain 48 are fixed to the rod ends of a pair of hydraulic cylinders 50, which are in turn pivotally connected to a bracket 52 fixed to the platform 16.

The delimbing platform 16 includes a first tubular member 54, which extends from the power unit 12 to a location just beyond the wheel 20 whereat it abuts in end-to-end relationship with a second tubular member 56. The members 54 and 56 are held together by a tubular insert 60, which is located half in the member 54 and half in the member 56. Fasteners, such as screws and bolts (not shown), secure the members 54 and 56 to each other and to the insert 60.-The platform 16 further includes a pair of guide tracks 62, which extend horizontally at its opposite sides along the length thereof. The tracks 62 are in the form of a first pair of channel members 64 which open outwardly from the opposite sides of the member 54 and a second pair of channel members 66 which open outwardly from the opposite sides of the member 56 and are in end-to-end abutment with the members 64. The break between that portion of the platform 16 including the tubular member 56 and the channel members 66, and the remainder of the platform, permits the member 56 to be disconnected from the member 54 to considerably shorten the length of the vehicle for transporting the latter over a highway, or the like, or between widely separated landing sites.

A delimbing head or carriage is indicated in its entirety by the reference numeral 68 and includes an integral frame 70 which is mounted in straddling relationship to, and for movement along, the delimbing platform '16. The frame 70 includes a pair of square tubes 72, at its opposite sides beside the guide rails 62. The opposite ends of the tubes 72 are each interconnected by a pair of longitudinally spaced, vertical plates 74, which bridge the platform 16. The frame 70 also includes a. plurality of support rollers 76, which are normally engaged with the bottom flanges of the tracks 62.

The rollers 76 are mounted, one each, at the opposite ends of first and second pairs of arms 78 respectively rockingly mounted through means of first and second pairs of longitudinally spaced, transverse pivot structures 80 in the tubes 72.

A delimbing blade assembly 82 is carried by the frame 72 and includes a plurality of blades arranged for receiving and encircling a tree stem to be delimbed. Specifically, the assembly 82 includes a pair of arcuate, plate-like blades 84 and 86 respectively fixed to the leading and trailing ends of the frame 70, with reference to it moving away from the power unit 12. The blades 84 and 86 are disposed concave upwardly and are mounted centrally above the platform 16, thus providing a bed for receiving and engaging the underside of a tree stem lying along the platform 16. Right and left longitudinally extending, horizontal pivot shafts 88 and 90 are journaled in the frame 72 at the opposite sides of the platform 16. Fixed to the shafts 88 and 90, at longitudinally offset locations, are right and left arms 92 and 94 to which are connected right and left blades 96 and 98, which are adapted for swinging transversely, with the arms, between an open, separated position (FIG. 8) defining a passage for permitting tree stems to be received on the fixed blades 84 and 86, and a closed position wherein the blades 96 and 98 cooperate with the blades 84 and 86 to grasp and encircle a tree stem. It is to be noted that the blades 84, 86, 96 and 98 are appropriately beveled at their leading and trailing edges so that limbs may be removed in either direction of movement of the delimbing head 68.

The right and left blades 96 and 98 each include inner and outer blade sections 100 and 102, to the backsides of which are respectively fixed pairs of spaced straps 104 and 106. The straps 106 extend inwardly beyond the inner ends of the outer blade sections 102 and are spaced so as to overlap the outer ends of the straps 104 and are pivotally connected thereto by means of pins 108, thus forming hinge connections between the blade sections 100 and 102. The arms 92 and 94 each include a pair of vertical, longitudinally spaced, triangular plates 110 having a web 112 integral with and joining their longest sides. The inner ends of the pairs of straps 106 are respectively pivotally mounted, as at pins 114, between intermediate corners of the pairs of plates 110. A pair of channel-like links 116 and 118 each have one end which straddles an intermediate point on, and is pivotally connected to, an associated pair of the straps 104, as at pins 120, and the opposite end of each of the links 116 and 118 straddles the outer corners of, and are pivotally connected to, the arms 92 and 94, as at pins 122. Biasing the pairs of links 116 and 118 outwardly about the pins 122 so as to dispose the inner and outer blade sections 100 and 102 to form a smooth, continuous are are a pair of tension springs 124 having their opposite ends connected to eye screws 126 located in the webs of the links 116 and 118 and to pins 128 received in ears 130 fixed to the webs .112 of the arms 92 and 94.,

The arms 92 and 94, hence the blades 96 and 98, are biased toward the closed position (FIG. 7) by springloaded structures including a pair of rods 132 associated with each arm and having one of their ends extending through apertures in the webs 112 and pivotally received on an associated pin 128. Compression springs 134 are received on the rods 132 and act between heads 136, at the free ends of the rods, and closed ends of tubes 138, which are coaxially received on the rods. The'pair'of tubes 138 associated with the i right arm 92 have their ends pivotally received on the left pivot shaft and the pair of tubes 138 associated with the left arm 94 have their ends pivotally received on the right pivot shaft 88.

For the purpose of opening the blades 96 and 98 against the bias of the springs 134, there is provided a power cylinder-operated blade opening assembly 139 including a rectangular housing 140 fixed crosswise to the platform 16 at a location not far removed from the power unit 12. Pivoted in the opposite ends of the housing 140 are a pair of pivot shafts 142 and 144, which are in axial alignment with pilot end portions of the shafts 88 and 90. A pair of cylindrical receptacles 148 and 15 0 are fixed to the ends of the shafts 142 and 144 and lugs 152 and 154 project first radially then axially from the receptacles. Extending radially from the pilot end portions of the shafts 88 and 90 and disposed for engagement by the operating lugs 152 and 154 are radially extending lugs 156 and 158. A hydraulic actuator 159 extends between and is pivotally connected to cranksll60 and 162 which project upwardly from the shafts 142 and 144. Thus, it can be seen that when the frame 72 is moved toward the assembly 139, the ends of the shafts 142and 144 will be received in the receptacles 148 and 150 and the lugs 156 and 158 will be located adjacent the inside of the lugs 152 and 154, as shown in FiG. 10. Extension of the actuator 159 will move the lugs 156 and 158 outwardly into engagement with the lugs 152 and 154 and cause the arms 92 and 94 and the associated blades 96 and 98 to move to the open position shown in FIG. 8.

A pair of spring-loaded stops 164 are fixed to the opposite sides of platform 16 adjacent the blade opening assembly 139 for limiting the movement of the delimbing head 68 toward the power unit 12 and a pair of spring-loaded stops 166 are mounted on the opposite sides of the platform 16 adjacent the end remote from the power unit 12 for establishing an outer limit for delimber head movement.

The delimbing head 68 is reversibly driven along the platform 16 between the pairs of stops 164 and 166 by means including a drive sprocket 170 rotatably mounted within the tubular platform member 54 adjacent the power unit 12 and a pulley 172 rotatably mounted at the end of the platform 16 remote from the power unit 12. A drive chain 174 having a length approximately the same as the platform 16 is meshed with the drive sprocket 170 and has an upper run which is received in a guide track 176 fixed centrally along the top of platform 16. The end link of the upper chain run is pinned, as at 178 to the trailing end of the frame 72. The lower run of the chain 174 extends within the tubular section 54 of the platform 16 and is secured at its end (not shown) to one end of a length of cable or wire rope 180. The cable 180 is received on the pulley 172 and is doubled back over the top of the platform 16. The end portion of thecable 180 is received in a tube 182, which is fixed centrally to the delimbing head frame 72. A clamp 184 on the cable 180 prevents the cable from being withdrawn from the tube 182. A reversible hydraulic motor 185 is drivingly connected to the sprocket 170 and it can be seen, that by driving the sprocket 170 so as to place the upper run of the chain 174 in tension, the delimbing head 68 will be advanced toward the power unit 12 and, that by driving the drive sprocket so as to place thelower run of the chain in tension, the delimbing head will be advanced away from the powerunit/ l A tree topping unit 186 is adjustably fixed to the end of the delimbing platform 16 remote from the power unit 12. The topping unit 186 includes a frame 188 having skirts 190, at its opposite sides, disposed alongside the tracks 62. Rollers 192 are mounted at the opposite ends of the skirts 190 and are disposed in the tracks 62. A pair of stops in the form of screws 194 are located in the upper flange of one of the tracks 62 at the opposite ends of one of the skirts 190 to hold the frame in a desired position. interconnecting the skirts 190 are a pair of vertical, longitudinally spaced plates 196, which bridge the platform 16. A bed structure 198 is integral with the top of the plates 196 and defines an opening 200 for receiving the top portion of a tree. A chain saw 202 includes a blade 204 which is vertically swingably mounted on the frame 188 in a position so as to traverse a treetop positioned in the opening 200. For this purpose, the drive housing of the saw 202- is fixed to a tubular rockshaft 206, which is journaled in the plates 196. A pair of sprockets 208 are fixed on the rockshaft 206 and have a pair of chains 210 engaged therewith. The chains 210 are also engaged with a pair of sprockets 212 fixed to a drive shaft 214,, which is journaled in the plates 196 below the rockshaft 206. A hydraulic actuator 216 is pivotally interconnected between a crank, fixed to the shaft 214, and the frame 188 and is operative upon extension to rotate the saw blade 204 toward a vertical, inoperative position, and is operative upon retraction to rotate the saw blade toward a horizontal, operative position. The saw cutting chain is driven by means of a hydraulic motor 218, which is drivingly connected through means of a chain 220 to a drive shaft 222, which is rotatably mounted within the rockshaft 206.

Trees are elevated from the ground to a delimbing and topping position on the platform 16 by means of a grapple and boom assembly 224. The assembly 224 includes a support post 226 which is mounted on the frame 14 of the power unit 12 for horizontal swinging movement about a vertical axis intersecting the longitudinal axis of the tubular delimbing frame section 54. A telescopic boom 227 having inner and outer sections 228 and 230, respectively, is pivoted at its inner end to the upper portion of the post 226. Fixed to the outer end of the boom section230 is a downwardly opening grapple 232 including a fixed tong 234 and a tong 236 mounted for pivotal swinging movement toward and away from the fixed tong. Fixed adjacent the outer end of the inner boom section 228 is a downwardly opening V-shaped heeling structure 238 and fixed adjacent the inner end of the boom section 228 is a downwardly projecting butt plate 240. v

The various elements of the boom and grapple assembly 224 are selectively positioned by a plurality of hydraulic actuations. More specifically, an actuator 242 is connected between the frame 14 and the post 226, a pair of actuators 244 are connected between the post 226 and the inner boom section 228, an actuator (not shown) is provided for telescopically moving the outer boom section 230 on the inner section 228 and an actuator 246 is connected between the, outer boom section 230 and the pivoted tong 232.

The power for operating all of the hydraulic functions associated with the vehicle 10 originates at an internal combustion engine 248, which is mounted on the frame 14 in a position to one side of the platform 16. The engine 248 is drivingly coupled to a pump 250 for supplying pressurized fluid to the various hydraulic functions through means of a manifold and hydraulic lines (not shown).

An operator's station 252 is mounted on the frame 14 to the opposite side of the platform 16 from the engine 248. Controls 254 are located at the station 252 and are representative of the many valve controls for selectively operating the various hydraulic functions. A pro-v tective framework 256 encloses the station 252 and is covered by a wire mesh screen 258.

In order to ready the delimbing machine 10 for delimbing operation, the machine 1.0 is first positioned alongside a pile of felled trees, with the wheels 18, 19 and 20 being turned to their working positions illustrated in FIG. 1 and with the power unit 12 being adjacent the butt ends of the trees. Next, the blades 96 and 98 of the delimbing head 68 are moved to their open position. This is accomplished by operating the delimbing head drive motor 183 to bring the pivot shafts 142 and 144 of the delimbing head 68 into register with the receptacles 148 and 150 of the blade-opening assembly 139. The blade-operating hydraulic actuator 159 is then extended to rotate the shafts 142 and 146 to engage the lugs 156 and 158 with the lugs 152 and 154 which causes rotation of the shafts 88 and 90 so as to swing the blade-carrying arms 92 and 94 away from each other until the blades 96 and 98 occupy the open position illustrated in FIG. 8. It is to be noted that the tension springs 124 maintain the outer blade sections 102 in their outermost position. The saw blade 204 is, at the same time, rotated to a substantially vertical position by extension of the hydraulic actuator 216. This provides access for placing a treetop in the opening 200 of the bed 198 of the topping unit 186. The platform 16 is then in condition for having a tree stem placed on top thereof.

To this latter end, the grapple and boom assembly is positioned, through selective actuation of the actuators 242, 244, 246 and the boom telescoping actuator (not shown), to place the grapple in grasping relationship to a selected tree stem. The stem is then manipulated until its end portion lies underneath the boom sections 228 and 230, with the butt being engaged with the plate 240. The tree stem is then shifted from the ground and since the majority of the weight of the tree stem lies beyond the grapple 232, it pivots downwardly about the grapple and, thus, remains engaged in the heel 238. When the tree stem is longitudinally aligned over the top of the platform 16, it is lowered onto the platform 16 with portions thereof being received in the delimbing head 68 and the topping unit 186. The bladeoperating actuator 159 is then retracted, permitting the pairs of compression springs 134 to act through the arms 92 and 94 to yieldingly engage the blades 96 and 98 with the tree stem, which blades cooperate with the fixed blades 84 and 86 to completely encircle the tree stem. The delimbing head motor 183 is then actuated to drive the head 68 towards the spring-loaded stops 166 adjacent the topping unit 186. As the delimbing head 68 advances along the tree stem, the beveled cutting edges along the leading edges of the blades 84, 86, 96 and 98 will cut limbs, by impact, from the stem. The hinged sections 100 and 102 of the blades 96 and 98 act to conform the blades more nearly to irregularities in the tree stem than would be possible if they were rigid blades. When the delimbing head 68 engages the stops 166, the motor 183 is reversed and stubs of branches remaining on the tree stem are removed as the head 68 travels towards the stops 164 to begin another cycle.

The chain saw drive motor 218 is actuated along with the saw swing motor 216 to swing the saw blade 204 downwardly to sever the top from the tree stem. When the top is free, the blade 204 is raised again by extension of the actuator 216.

After the delimbing head 68 is again operatively coupled with the blade opening assembly 139, the actuator 159 is extended to open the blades 96 and 98.

The boom and grapple assembly 224 is then swung to deposit the delimbed and topped stem along the delimbing platform 16 at the side opposite from the unprocessed pile of trees.

The above delimbing and topping procedure is repeated until the entire pile is processed. The vehicle 10 is advanced into the pile by simultaneously actuating the wheel drive motors 30 and 42 for the wheels l8, l9 and 20.

Should it be desired to move the machine 10 endwise in positioning the machine at various piles at a landing site, the lock pins (not shown) fixing the wheel spindles 22 to the frame 14 are disengaged and the motors 30 are actuated to drive the wheels 18 and 19 about their respective spindle axis. When the wheels 18 and 19 are in the transport position, the lock pins are again'engaged.

If the machine 10 is to be transported any appreciable distance overland, it may be desirable or necessary to shorten its length. To do this, the fasteners (not shown) securing the tubular frame members 54 and 56 to each other and to the tubular insert 60 are loosened. The drive cable 180 is disconnected from the delimbing head 68 and is disengaged from the pulley 172. A logging tractor or some other vehicle is connected in supporting and endwise-pulling relationship to the frame member 56 and is operated to separate the frame memher 56 from the member 54. The separated frame member 56 then is loaded aboard a truck, or the like, for transport to the desired site where it is again rejoined with the frame member 54.

We claim:

1. In a tree stem delimbing assembly of the type including a plurality of delimbing blades mounted and arranged for cooperatively encircling a tree stem and for removing limbs therefrom upon there being relative movement between the blades and the tree stem lengthwise of the tree stem, an improved blade arrangement comprising: a support frame; a first pair of arcuate plate-like blades fixed in alignment onsaid supporting frame and being disposed to engage spaced areas along one side of a tree stem; a pair of pivot arms pivotally mounted on said frame on opposite sides of and for swinging movement crosswise to the alignment of said first pair of blades; a second pair of arcuate plate-like blades respectively pivotally connected to said arms; a pair of links pivotally interconnected between said arms and said second pair of blades; means biasing said pair of arms toward the alignment of said first pair of blades; said arms being movable against the bias means to a position permitting said first pair of blades to embrace a tree stem; and said arms and said second pair of blades being so spaced relative to each other and to said first pair of blades that the pairs of blades cooperate to encircle a tree stem embraced by said first pair of blade segments. 8

2. The invention defined in claim 1 wherein said second pair of blades include inner and outer hingedly interconnected sections and said arms being pivotally interconnected to said inner sections and said links being pivotally interconnected to said outer sections.

3. The invention defined in claim 1 wherein the pivotal mounting of said pair of arms includes a pair of pivot rods extending parallel to and on opposite sides of the alignment of said first pair of blade segments and being journaled on said frame, said pair of arms being respectively fixed to said pair of pivot rods and lug means fixed to said pivot rods and being adapted for engagement by power means for moving said arms against said bias means.

4. The invention defined in claim 3 wherein said bias means includes a first compression spring assembly operatively connected between one pivot rod and the arm that is fixed to said other pivot rod; and a second compression spring assembly operatively connected between said other pivot rod and the arm that is fixed to said one pivot rod.

5. The invention defined in claim 2 and further including a pair of tension springs respectively connected between said pair of links and said pair of arms; and the hinge connections between said inner and outer blade sections of said second pair of blades being so disposed said direction of movement; a pair of links respectively forming articulated extensions of said pair of levers; a second pair of curved plate-like blades pivotally interconnected between a respective lever and link; and means biasing said levers towards each other about their pivotal connection to said frame for engaging said second pair of blades with a tree :stem engaged by said relative to the pivot connections between said pair of arms and said pair of links that said tension springs urge the hinged-together blade segments towards a position wherein the curvature of the blades is smooth and continuous.

6. The invention defined in claim 1 wherein said pair of fixed blades are spaced in the direction of relative movement between the blades and the tree stem and wherein said pair of arms are located between said fixed blades.

7. A delimbing structure adapted for linear movement along a tree stem comprising: a supporting frame; a first pair of curved plate-1ike blades fixed to said frame at spaced locations aligned in said direction of movement and being disposed for embracing and delimbing one side of a tree stem; a pair of levers pivotally mounted on opposite sides of said frame at locations spaced in, andfor swinging movement crosswise to,

first pair of blades.

8. The invention defined in claim 5 wherein said second pair of blades each includes inner and outer hingedly interconnected sections with said outer sections being pivotally connected to a respective link and said inner sections being pivotally connected to a respective lever.

9. The invention defined in claim 5 wherein a pair of parallel rockshafts are journaled in opposite sides of said frame; said pair of levers respectively being fixed to said pair of rockshafts; and said rockshafts including means engageable with power means for causing rotation of said rockshafts for moving said pair of levers against said biasing means.

10. The invention defined in claim 7 wherein said biasing means includes a pair of spring-loaded telescopic assemblies pivotally interconnected between said levers and the pivot shaft located at the side of the frame opposite from the lever.

(The invention defined in claim 6 wherein a pair of tension springs are connected between said links and said levers so as to bias said links away from each other. 

1. In a tree stem delimbing assembly of the type including a plurality of delimbing blades mounted and arranged for cooperatively encircling a tree stem and for removing limbs therefrom upon there being relative movement between the blades and the tree stem lengthwise of the tree stem, an improved blade arrangement comprising: a support frame; a first pair of arcuate plate-like blades fixed in alignment on said supporting frame and being disposed to engage spaced areas along one side of a tree stem; a pair of pivot arms pivotally mounted on said frame on opposite sides of and for swinging movement crosswise to the alignment of said first pair of blades; a second pair of arcuate plate-like blades respectively pivotally connected to said arms; a pair of links pivotally interconnected between said arms and said second pair of blades; means biasing said pair of arms toward the alignment of said first pair of blades; said arms being movable against the bias means to a position permitting said first pair of blades to embrace a tree stem; and said arms and said second pair of blades being so spaced relative to each other and to said first pair of blades that the pairs of blades cooperate to encircle a tree stem embraced by said first pair of blade segments.
 2. The invention defined in claim 1 wherein said second pair of blades include inner and outer hingedly interconnected sections and said arms being pivotally interconnected to said inner sections and said links being pivotally interconnected to said outer sections.
 3. The invention defined in claim 1 wherein the pivotal mounting of said pair of arms includes a pair of pivot rods extending parallel to and on opposite sides of the alignment of said first pair of blade segments and being journaled on said frame, said pair of arms being respectively fixed to said pair of pivot rods and lug means fixed to said pivot rods and being adapted for engagement by power means for moving said arms against said bias means.
 4. The invention defined in claim 3 wherein said bias means includes a first compression spring assembly operatively connected between one pivot rod and the arm that is fixed to said other pivot rod; and a second compression spring assembly operatively connected between said other pivot rod and the arm that is fixed to said one pivot rod.
 5. The invention defined in claim 2 and further including a pair of tension springs respectively connected between said pair of links and said pair of arms; and the hinge connections between said inner and outer blade sections of said second pair of blades being so disposed relative to the pivot connections between said pair of arms and said pair of links that said tension springs urge the hinged-together blade segments towards a position wherein the curvature of the blades is smooth and continuous.
 6. The invention defined in claim 1 wherein said pair of fixed blades are spaced in the direction of relative movement between the blades and the tree stem and wherein said pair of arms are located between said fixed blades.
 7. A delimbing structure adapted for linear movement along a tree stem comprising: a supporting frame; a first pair of curved plate-like blades fixed to said frame at spaced locations aligned in said direction of movement and being disposed for embracing and delimbing one side of a tree stem; a pair of levers pivotally mounted on opposite sides of said frame at locations spaced in, and for swinging movement crosswise to, said direction of movement; a pair of links respectively forming articulated extensions of said pair of levers; a second pair of curved plate-like blades pivotally interconnected between a respective lever and link; and means biasing said levers towards each other about their pivotal connection to said frame for engaging said second pair of blades with a tree stem engaged by said first pair of blades.
 8. The invention defined in claim 5 wherein said second pair of blades each includes inner and outer hingedly interconnected sections with said outer sections being pivotally connected to a respective link and said inner sections being pivotally connected to a respective lever.
 9. The invention defined in claim 5 wherein a pair of parallel rockshafts are journaled in opposite sides of said frame; said pair of levers respectively being fixed to said pair of rockshafts; and said rockshafts including means engageable with power means for causing rotation of said rockshafts for moving said pair of levers against said biasing means.
 10. The invention defined in claim 7 wherein said biasing means includes a pair of spring-loaded telescopic assemblies pivotally interconnected between said levers and the pivot shaft located at the side of the frame opposite from the lever.
 11. The invention defined in claim 6 wherein a pair of tension springs are connected between said links and said levers so as to bias said links away from each other. 